1. Field
Example embodiments relate to photoelectronic devices including a charge barrier configured to repress moving of charges generated by an optical absorption layer.
2. Description of the Related Art
A photoelectronic device uses photoelectronic effect and includes a photo-detector, a phototransistor, and a solar cell, etc.
A photo-detector of the related art includes a silicon p-n junction. As the pixel size becomes as small as approximately 1 μm, an amount of received light is reduced. Also, due to the limit of the band gap (1.1 eV) of silicon, an amount of received light in a near infrared region (˜850 nm) is relatively small. Accordingly, the sensitivity of optical detection is reduced when the intensity of illumination is relatively low and in the near infrared region.
Recently, a photo-detector that includes graphene and transition metal dichalcogenide (TMD) has been developed. This photo-detector has a thickness of a few nm and relatively high photo sensitivity. The TMD material has an optical absorption rate one hundred times greater than that of silicon. Thus, although the TMD material is relatively thin, the TMD material has a relatively high optical detection efficiency. Single-layered graphene has a surface resistance of approximately 100 ohm/sq and a light absorption rate of 2.3%, and thus, may be used as a transparent electrode.
In a photo-detector that includes TMD, the TMD absorbs light, and electrons and holes generated accordingly move to electrodes (for example, graphene) formed on both sides of the TMD.
At this point, even though light is not irradiated to the TMD, a dark current may flow therethrough according to a voltage applied to the electrodes. The dark current may act as signal noise, and thus, the sensitivity of detection of the photo-detector may be reduced.